In the field of electrical contracting, it is often necessary for a piece of equipment, such as an electrical panel or a conduit, to be mounted to the outside of a metal building. However, problems arise in many cases where the equipment will not mount flush against the metal wall siding panel, because the metal siding includes vertical ribbing that protrudes from the wall. This vertical ribbing prevents flush mounting of the equipment, especially with respect to pieces of equipment having a substantial width. The problem similarly exists with respect to metal wall siding panels that have incremental ribs with varying degrees of protrusion from the wall.